1. Field of the Invention
The present invention relates to a display panel and an upper substrate thereof, and particularly to a plasma display panel (PDP) and an upper substrate thereof.
2. Description of Related Art
As an important human-computer interface, the flat display can be categorized into several kinds, such as plasma display panel (PDP), organic electro-luminescent display (OLED), liquid crystal display (LCD) and light emitting diode (LED) display. PDPs, with such advantages of larger size, self-illumination, no view angle dependence, thinness and full color display, have the potential to become a mainstream flat display of the next generation.
Generally, PDPs apply the characteristic in a phosphor material or a fluorescent material which can emit a visible light when illuminated by an ultraviolet light. The PDP light-emitting structure generally comprises a pair of electrodes (anode electrode and cathode electrode), a discharging gas and a phosphor layer (or a fluorescent layer). When a voltage applied between the anode electrode and the cathode electrode exceeds a firing value of the discharge gas, the discharging gas discharges and emits an ultraviolet light. The ultraviolet light illuminates the phosphor layer (or the fluorescent layer), and the phosphor layer (or the fluorescent layer) is then excited to an excited state. During a subsequent process when the phosphor layer (or the fluorescent layer) returns from the excited state back to a ground state, the phosphor layer (or the fluorescent layer) emits visible lights of different colors according to different material characteristics of the phosphor layer (or the fluorescent layer). This is a light emitting principle of a typical PDP.
According to a color reproducibility specification established by the National Television System Committee (NTSC), in order to obtain a white light having a high color temperature, the luminance requirement for the red light, green light and blue light which are combined into such a white light are different. Since images with higher color temperatures appear sharper image quality in human eyes, PDPs are developing to produce images having higher color temperatures.
FIG. 1 is a schematic structural view of a conventional PDP. Referring to FIG. 1, the conventional PDP 40 includes an upper substrate 10, a lower substrate 20, and a discharging gas 30 filled between the upper substrate 10 and the lower substrate 20.
The upper substrate 10 includes a glass substrate 11, a plurality of transparent electrodes 12, a plurality of bus electrodes 13, a transparent dielectric layer 14 and a protective layer 15. The transparent electrodes 12 are disposed on the glass substrate 11, and the bus electrodes 13 are disposed on the transparent electrodes 12. The transparent electrodes 12 and the bus electrodes 13 are arranged along an X-direction, configuring a plurality of scan electrodes 16 and a plurality of common electrodes 17 disposed alternately. The transparent dielectric layer 14 is disposed on the glass substrate 11 and covers the scan electrodes 16 and the common electrodes 17. The protective layer 15 is disposed on the transparent dielectric layer 14.
The lower substrate 20 includes a glass substrate 21, a plurality of data electrodes 22, a white dielectric layer 23, a rib structure 24 and a fluorescent layer 25. The data electrodes are disposed on the glass substrate 21, and are arranged along a Y-direction. The white dielectric layer 23 is disposed on the glass substrate 21 and covers the data electrodes 22. The rib structure 24 is disposed on the white dielectric layer 23, and defines a plurality of discharging spaces 24r, 25g, 24b, with the upper substrate 10. In the discharging spaces 24r, 24g, 24b, and the rib structure 24 respectively has corresponding fluorescent materials 25r, 25g, 25b for respectively emitting a red light, a green light and a blue light.
The discharging gas 30 is disposed in the discharging spaces 24r, 24g, 24b, defined by the upper substrate 10 and the rib structure 24 of the lower substrate 20.
When an appropriate voltage is applied to the scan electrodes 16, the common electrodes 17 and the data electrodes 22, the discharging gas 30 disposed in the discharging spaces 24r, 24g, 24b is ionized into a plasma, where the atoms of the discharge gas collided with high energy electrons are at an excited state. When returning from the excited state back to a ground state, the atoms emit ultraviolet lights. The ultraviolet lights illuminate the fluorescent materials 25r, 25g, 25b, and the fluorescent materials 25r, 25g, 25b then respectively emit a red light, a green light and a blue light, all of which are adapted to be combined into a white light.
FIG. 1B are top views illustrating scan electrodes and common electrodes of three adjacent discharging spaces. Referring to FIG. 1B, the structures of the scan electrodes 16 and the common electrodes 17 in the discharging spaces 24r, 24g, 24b are the same, and therefore the red light, the green light and the blue light emitted by the fluorescent materials 25r, 25g, 25b can be adjusted in a limited range. Therefore, the light intensity ratio of the red light, the green light and the blue light is not optimal, and accordingly they can not be combined into a white light having a higher color temperature.
There are some other designs of scan electrodes and common electrodes to counter the above disadvantages. FIG. 1C is a top view of another conventional structure of scan electrodes and common electrodes. Referring to FIG. 1C, in order to have the PDP 40 emit a white light with higher color temperature, this conventional design employs arborized electrodes 18r, 18g, 18b to replace the foregoing transparent electrodes 12 disposed in the discharging spaces 24r, 24g, 24b. A white light having higher color temperature can be obtained by adjusting the number of the arborized electrodes 18r, 18g, 18b. However, the branches of the arborized electrodes 18r, 18g, 18b are relatively thin in line width, and accordingly the connecting sessions 18a connecting the bus electrodes 13 and the arborized electrodes 18r, 18g, 18b are likely to break during the fabricating process. The discharging spaces with broken arborized electrodes 18r, 18g, 18b cannot display normally.